Night vision devices are commonly used by military personnel for conducting operations in low light or night conditions. The night vision devices utilized by the military typically include image intensifier tubes and associated optics that convert infrared and near infrared light into viewable images. A common night vision device currently being used in the U.S. Army is the PVS7 night vision device, manufactured by ITT Corporation in Roanoke, Va.
Assemblies for mounting night vision devices to a helmet are well-known in the art. These mounting assemblies allow a user's hands to remain free while viewing a scene through the night vision device. Prior art mounting assemblies typically include one or more of the following features: positional adjustment of the night vision device between a use and stowed position; tilt angle adjustment of the night vision device relative to the user's eyes; focal adjustment of the location of the night vision device relative to the user's eyes; and automatic shutdown of the night vision device when not in the use position.
A known mounting assembly for night vision devices encompasses a flip-up helmet mount that attempts to provide all of the features identified above. However, in that device, the automatic shutdown assembly may be triggered while the user is performing certain combat maneuvers. More particularly, the automatic shutdown assembly includes a magnet module having a vertically extending oval-shaped cavity. A long, narrow bar-shaped magnet is disposed within the cavity and translates from one end of the cavity to an opposite end of the cavity by gravity. The night vision device is turned on when the magnet is at an end of the cavity immediately adjacent to a magnetically responsive switch. The night vision device is automatically turned off when the magnet is moved to an opposite end of the cavity where the magnet is sufficiently displaced from the switch.
It is important that the night vision device turn off when flipped up. The combination of an elongated cavity for movement of long, narrow bar magnet within results in an automatic shutdown assembly with excellent reliability. However, when the operator performs certain combat maneuvers, such as a lateral roll, the bar magnet, under the influence of gravity, can easily move between both ends of the cavity. Thus, the automatic shutdown assembly may intermittently turn the goggles off in use or on while not in use due to inadvertent movement of the magnet caused by movement of a person wearing the goggles. This is undesirable since a user's “night vision” and safety may be affected during a critical moment of combat.
Thus, there is a need for an improved magnet module which operates reliably during movement of the night vision device from use to stowed position but does not inadvertently operate during certain combat maneuvers and which addresses these and other problems that exist with flip-mount helmet mounts for night vision devices disclosed in the prior art.